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28 lines
1.1 KiB
Racket
28 lines
1.1 KiB
Racket
#lang reader "../aoc-lang.rkt"
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(provide (rename-out [#%mb #%module-begin]) ★ ★★)
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(define-macro (#%mb (STARS) (Generator X starts with NUM) ...)
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#`(#%module-begin
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(apply STARS '(NUM ...))))
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(define (lower-16-bits x) (bitwise-bit-field x 0 16))
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(define (generator-base a b rounds [modulo-a 1] [modulo-b 1])
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(for/fold ([a-last a]
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[b-last b]
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[sum 0]
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#:result sum)
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([i (in-range rounds)])
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(define a (for/fold ([a a-last])
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([i (in-naturals)]
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#:break (and (positive? i) (zero? (modulo a modulo-a))))
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(remainder (* 16807 a) 2147483647)))
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(define b (for/fold ([b b-last])
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([i (in-naturals)]
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#:break (and (positive? i) (zero? (modulo b modulo-b))))
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(remainder (* 48271 b) 2147483647)))
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(values a b (+ sum (if (= (lower-16-bits a) (lower-16-bits b)) 1 0)))))
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(define (★ a-start b-start) (generator-base a-start b-start 40000000))
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(define (★★ a-start b-start) (generator-base a-start b-start 5000000 4 8)) |